I started out by using a gray, spray paint primer on the coffee cans, then my kids and I simply painted them using outdoor paints. Use your imagination. Once the paint was dry, I sealed the cans with a few layers of a clear, acrylic spray.
Once your frog house is ready, find a spot in your garden for it. Frogs and toads prefer someplace that is moist and shady. Lay the can on it's side and bury half of it, filling the inside partially so any visiting frogs will be sitting on dirt.
It's as simple and easy as that.